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A carbon sink is a natural or artificial reservoir that accumulates and stores some carbon-containing chemical compound for an indefinite period. The process by which carbon sinks remove carbon dioxide (CO2) from the atmosphere is known as carbon sequestration. Public awareness of the significance of CO2 sinks has grown since passage of the Kyoto Protocol, which promotes their use as a form of carbon offset. There are also different strategies used to enhance this process. The natural sinks are: * Absorption of carbon dioxide by the oceans via physicochemical and biological processes * Photosynthesis by terrestrial plants Natural sinks are typically much bigger than artificial sinks. The main artificial sinks are: * Landfills〔(【引用サイトリンク】title=Environmental Research and Education Foundation )〕〔http://epa.gov/epawaste/conserve/tools/warm/pdfs/landfill-carbon-storage-in-warm10-28-10.pdf〕 * Carbon capture and storage proposals Carbon sources include: * Combustion of fossil fuels (coal, natural gas, and oil) by humans for energy and transportation * Fires (by combustion) * Farmland (by animal respiration); there are proposals for improvements in farming practices to reverse this. == Kyoto Protocol == Because growing vegetation takes in carbon dioxide, the Kyoto Protocol allows Annex I countries with large areas of growing forests to issue Removal Units to recognize the sequestration of carbon. The additional units make it easier for them to achieve their target emission levels. It is estimated that forests absorb between 10 and 20 tons of carbon dioxide per hectare each year, through photosynthetic conversion into starch, cellulose, lignin, and wooden biomass. While this has been well documented for temperate forests and plantations, the fauna of the tropical forests place some limitations for such global estimates. Some countries seek to trade emission rights in carbon emission markets, purchasing the unused carbon emission allowances of other countries. If overall limits on greenhouse gas emission are put into place, cap and trade market mechanisms are purported to find cost-effective ways to reduce emissions. There is as yet no carbon audit regime for all such markets globally, and none is specified in the Kyoto Protocol. National carbon emissions are self-declared. In the Clean Development Mechanism, only afforestation and reforestation are eligible to produce certified emission reductions (CERs) in the first commitment period of the Kyoto Protocol (2008–2012). Forest conservation activities or activities avoiding deforestation, which would result in emission reduction through the conservation of existing carbon stocks, are not eligible at this time. Also, agricultural carbon sequestration is not possible yet. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Carbon sink」の詳細全文を読む スポンサード リンク
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